In the technical field of color matching, it is a key technique to dispense quantitative colorant by means of a reciprocating pump. At present, piston pumps, plunger pumps, folding pumps and the like are common reciprocating positive displacement pumps. Each of the pumps generally consists of a cylinder, a piston rod, a piston, and a colorant outlet, with the piston pump as an example. A strict requirement is made to the volume of a colorant in color matching, i.e., a requirement that an error of the dispensed volume of a colorant cannot exceed a certain percentage (e.g., less than 1%) when a pump dispenses abundant colorant (e.g., greater than 15 ml), and an error of the dispensed volume of a colorant cannot exceed a certain percentage (e.g., less than 12%) either with regard to the dispensing of a trace amount of colorant (e.g., less than 0.5 ml). To achieve this objective, two colorant dispensers may be used: one is a colorant dispenser consisting essentially of a large pump that is mainly used for dispensing abundant colorant, and the other one is a colorant dispenser consisting essentially of a small pump that is mainly used for dispensing a trace amount of colorant; alternatively, a pair of pumping-out systems of both abundant dispensing and trace amount of dispensing are disposed in parallel by connecting a large pump having a large-section cylinder with a small pump having a small-section cylinder in parallel in the same pump. The above-mentioned methods both have the problems of large occupied space, complicated structure, and high cost; therefore, a small piston rod may be fixedly connected under a piston rod with a small cylinder matching with a small reciprocating lever being disposed in a cylinder and provided with a colorant outlet, and then the objective of dispensing of abundant colorant or a trace amount of colorant is achieved by means of the reciprocating motion of the large piston rod and the small piston rod (taking, but not limited to, a piston pump for example). However, a three-way change valve applicable to general colorant dispensing pumps, when applied to such a pump capable of dispensing abundant colorant as well as a trace amount of colorant, cannot meet the requirements for use. A change valve, which is disclosed in patent No. CN201310045508.9, may effectively solve the problems of colorant drying and hardening at a colorant outlet and colorant deposition in a colorant outlet pipe with improved colorant dispensing accuracy, but it cannot meet the requirements for use of such a pump capable of dispensing abundant colorant as well as a trace amount of colorant.